Music by Kevin MacLeod. Available under the Creative Commons Attribution 3.0 Unported license. Download link: https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100505

MacLeod's description:

Genre: Unclassifiable
Length: 3:08
Instruments: Piano, Cello

An interesting jumble of cello and some piano fused together to create an eerie and intense piece the likes of which no one has ever heard of...until now.
ISRC: US-UAN-11-00505
Eerie, Intense, Suspenseful, Unnerving 2008